Fire,
a female, was shot in Utah, and later survived West Nile virusPhotos by Steve Hall

Swainson's Hawk

Buteo SwainsoniOrder:
FalconiformesFamily:
Accipitiridae
Genus: Buteo

A medium
sized buteo from
western North
America, named for 19th century British naturalist William Swainson,
immature Swainson's are
often mistaken
for young red tails.However, they are
smaller, their wings are proportionally slightly longer, more slender
and more
pointed than
the red tail’s, and they fly with their wings in a slight dihedral,
tipping back and forth while soaring. The Swainson's talons are also
smaller than the red-tail's.

Swainson's hawks
gather in groups called kettles, to make the longest
migration of any hawk, up to 17,000 miles round trip from Canada to
the Pampas of Argentina.
They have an efficient migration method, soaring up on warm thermal
currents, gliding gradually down to the next thermal, gaining
considerable
speed,
and then beginning the process again.As
soaring and gliding take very little energy, it is truly the lazy
bird’s key to
migration. Since the migrating Swainson's tend to group up, head
towards, and follow the land bridge of Panama on their way south, these
birds can be seen in flocks numbering in the thousands. Radio telemetry
and banding have greatly enhanced our
knowledge of the Swainson's migration specifically, and their movements
generally.

The Swainson's hawk
eats more insects than
other buteos do, often grabbing them on the wing, principally
grasshoppers, crickets, dragonflies and locusts, and is
sometimes called the grasshopper hawk. Insects make up almost of their
diet in their Winter habitats.The Swainson's diet requires more nutritious foods while nesting and feeding their young, so they add rodents,
rabbits and reptiles while on the American and Canadian deserts, grasslands and praries,
and have been known to
stand in groups at the mouths of
ground squirrel
burrows and grab squirrels as they emerge. Swainsons
defend Spring and Summer territories of about two square miles, not
only against other Swainsons, but sometimes against Red-Tailed Hawks
and Ferruginous Hawks.

Swainson's nest in trees, shrubs and on cliff edges, so the continuing
conversion of the Plains habitat to grazing land, alfalfa and wheat
(which affords cover to their prey), combined with the destruction of
the few sparse trees by cattle continually rubbing against their
trunks, and converting the areas around the tree's base to muddy
wallows, have made locating suitable nesting sites more challenging. Swainsons arrive at the nesting grounds in March and April,
and spend a week or so building their nests. Nests are constructed of
twigs and sticks, and from the one to four eggs laid a few days apart,
chicks emerge with a similar time gap, with the result that older
chicks are larger and more likely to survive by appropriating more of
the
rodents adults bring to the nest and shred for the chicks.

The Swainson's hawk is
vulnerable to pesticide poisoning in its
wintering grounds on the Pampas in Argentina, where it feeds on
grasshoppers, and where pesticides, such as DDT, long since
banned in the United
States are still used. As the
birds roost and hunt together in huge flocks in Winter, they are
sometimes inadvertently blanketed by the aerial pesticide spraying,
causing mass die-offs, including two severe seasons in 1995 and 1996
when thousands of Swainsons died. In an
encouraging development, Argentine farmers and Ciba Geigy, a
manufacturer of the relatively inexpensive but lethal pesticide
monocrotophos, which has
been directly linked to Swainson's mortality, have cooperated
with raptor
biologists from Canada, America and Argentina in an effort to use less
lethal pesticides (which still have the effect of depriving the
Swainson's of their natural prey), and restrict where monocrotophos
is used.

Nevertheless, the Swainson's, partly because of the
situation on the Pampas, but also because of the decline of Richardson
ground squirrels and other small plains rodents in the US, is in
general decline throughout
its range. Fire was
shot by some moron in Utah, and later survived West Nile virus during
its recovery period. Watch the video linked below for a fascinating
documentary on the Swainson's hawk.